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Vivek Sharma

Publications and source records attributed to Vivek Sharma.

At least 19 recordsLinked to original sources
PubMed2025

Decoding the distribution, structure-function-redox potential relationship and recent advances in fungal laccases: a systematic approach.

Laccases, categorized as multicopper oxidases, are recognized for their multifaceted roles in ecosystems and their utility in diverse industrial applications. Laccases from higher fungi, specifically Ascomycota and Basidiomycota, have garnered significant research interest due to their elevated redox potentials and their capacity to degrade lignin in decaying wood, alongside other industrial uses. Here, we have conducted a comprehensive and systematic analysis on fungal laccases using Web of Science, Scopus, PubMed, and ScienceDirect. The genomic distribution, phylogenetic affiliation, and structural organization of laccase-encoding genes in higher fungal species were investigated, as were the catalytic mechanisms of the corresponding enzymes. Additionally, the study explores the correlation between structural domains and redox potential, as well as the impact of post-translational modifications like glycosylation on enzyme activity. Furthermore, the recent advancements in laccase engineering, employing strategies such as rational design, directed evolution, and heterologous expression are discussed. The review also explores the scope of "artificial intelligence and machine learning" in deducing the structure-function relationships, optimizing codon usage, predicting signal peptides, enhancing enzymatic performance, and developing host-specific genetic engineering techniques is also discussed for tailoring fungal laccases to meet the demands of industrial biocatalysis for improved activity and stability.

Laccase↗
PubMed2007

Proinflammatory mediators released by activated microglia induces neuronal death in Japanese encephalitis.

While a number of studies have documented the importance of microglia in central nervous system (CNS) response to injury, infection and disease, little is known regarding its role in viral encephalitis. We therefore, exploited an experimental model of Japanese Encephalitis, to better understand the role played by microglia in Japanese Encephalitis Virus (JEV) infection. Lectin staining performed to assess microglial activation indicated a robust increase in reactive microglia following infection. A difference in the topographic distribution of activated, resting, and phagocytic microglia was also observed. The levels of various proinflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (Cox-2), IL-6, IL-1beta, TNF-alpha, and MCP-1 that have been implicated in microglial response to an activational state was significantly elevated following infection. These cytokines exhibited region selective expression in the brains of infected animals, with the highest expression observed in the hippocampus. Moreover, the expression of neuronal specific nuclear protein NeuN was markedly downregulated during progressive infection indicating neuronal loss. In vitro studies further confirmed that microglial activation and subsequent release of various proinflammatory mediators induces neuronal death following JEV infection. Although initiation of immune responses by microglial cells is an important protective mechanism in the CNS, unrestrained inflammatory responses may result in irreparable brain damage. Our findings suggest that the increased microglial activation following JEV infection influences the outcome of viral pathogenesis. It is likely that the increased microglial activation triggers bystander damage, as the animals eventually succumb to infection.

Animals↗
PubMed2006

Diversity and differentiation among fluorescent pseudomonads in crop rhizospheres with whole-cell protein profiles.

Fluorescent pseudomonads from rhizospheres of four different crops, grown under similar soil and climatic conditions were phenotypically characterized to differentiate them into biovars. In protein electrophenogram studies of relationships among fluorescent pseudomonads by UPGMA cluster analysis based on DICE similarity index, the isolates were mainly discerned into three major clusters representing four different biovars. The biovars generally matched the delineated phenotypic clusters with the exception of a strain belonging to biovar II. However, the isolates representing similar rhizospheres and geographic locations were generally distributed into different phenotypic clusters as influenced by factors yet to be determined. The studies reinstated the importance of whole-cell protein analyses in characterizing pseudomonads and assessing their diversity.

Bacterial Proteins↗
PubMed2006

Chaotic mixing in microdroplets.

We describe a general methodology for introducing thorough chaotic mixing in microdroplets. The mixing properties of fluid flows in microdroplets are governed by their symmetries, which give rise to invariant surfaces serving as barriers to transport. Complete three-dimensional mixing by chaotic advection requires destruction of all flow invariants. To illustrate this idea, we demonstrate that complete mixing can be obtained in a time-dependent flow produced by moving a microdroplet along a two-dimensional path. The theoretical predictions are confirmed by experiments that use the thermocapillary effect to manipulate microdroplets.

Diffusion↗
PubMed2006

Sequence analysis of the cbb3 oxidases and an atomic model for the Rhodobacter sphaeroides enzyme.

The cbb3-type oxidases are members of the heme-copper oxidase superfamily, distant by sequence comparisons, but sharing common functional characteristics. To understand the minimal common properties of the superfamily, and to learn about cbb3-type oxidases specifically, we have analyzed a wide set of heme-copper oxidase sequences and built a homology model of the catalytic subunit of the cbb3 oxidase from Rhodobacter sphaeroides. We conclude that with regard to the active site surroundings, the cbb3 oxidases greatly resemble the structurally known oxidases, while major differences are found in three segments: the additional N-terminal stretch of ca. 60 amino acids, the segment following helix 3 to the end of helix 5, and the C-terminus from helix 11 onward. The conserved core contains the active site tyrosine and also an analogue of the K-channel of proton transfer, but centered on a well-conserved histidine in the lower part of helix 7. Modeling the variant parts of the enzyme suggests that two periplasmic loops (between helices 3 and 4 and between helices 11 and 12) could interact with each other as a part of the active site structure and might have an important role in proton pumping. An analogue of the D-channel is not found, but an alternative channel might form around helix 9. A preliminary packing model of the trimeric enzyme is also presented.

Amino Acid Sequence↗
PubMed2005

A low-cost, portable generic biotoxicity assay for environmental monitoring applications.

Fish chromatophores have been shown to be promising biosensors for the detection of hostile agents in the environment. However, state-of-art methods for such applications are still based on extensive use of data/signal processing, in conjunction with need for a skilled human observer to carry out the detection. As a result, conventional methods are complex, costly and cumbersome rendering them useless for field applications requiring low-cost portable solutions capable of fast detection. A new technique is proposed based on the popular scheme of observing the aggregation response in chromatophores for detection of toxicity, and a solution using optical detection and electronic processing is outlined. This scheme has the advantage of being low in cost while providing simple, fast and reliable detection.

Animals↗
PubMed2005

Symptomatic portal system thrombosis in soldiers due to extended stay at extreme altitude.

BACKGROUND: With induction of Indian Army to heights over 5000 m above mean sealevel (MSL), several new complications of long-term stay at extreme altitude have come to light. The authors' experience with soldiers who developed symptomatic portal system thrombosis (SPST) is described here. METHODS: Clinical data were prospectively collected between April 1998 and April 2003, on all patients hospitalized for SPST from high-altitude areas (HAA, >3000 m above MSL) and those from non-high-altitude areas (NHAA). Site of thrombosis was confirmed by imaging and included splenic, portal, superior mesenteric, or inferior mesenteric vein thrombosis. Patients were investigated to rule out known predisposing factors and prothrombotic conditions. RESULTS: A total of 37 cases of SPST were seen during the study period, of which 26 were from HAA. Mean age of cases from HAA was 27 +/- 4.6 years and all were male. Mean stay at high altitude was 11.7 +/- 6.2 months. First symptom was pain in abdomen in almost all the cases, later followed by gastrointestinal bleeding and fever in 14 each, and vomiting in 19. Clinical examination showed ascites (81%), splenomegaly (76.9%), and hepatomegaly (69.2%). Diagnosis was made by imaging scans (23 cases) and on surgery in three cases. A known prothrombotic state was detected in five cases from HAA and in eight cases from NHAA (P < or = 0.01). Ultrasound Doppler scan picked up collaterals as early as 12-45 days after onset of symptoms. CONCLUSIONS: Extended stay at HAA may be a risk factor for development of symptomatic portal system thrombosis.

Adult↗
PubMed2004

TB drug discovery: addressing issues of persistence and resistance.

Tuberculosis remains a leading cause of mortality worldwide into the 21st century. Among the main obstacles to the global control of the disease are emerging multi-drug resistant strains and the recalcitrance of persistent infections to treatment with conventional anti-TB drugs. Here we review recent developments in our understanding of some of the pathways involved in a persistent infection and pathogenesis of Mycobacterium tuberculosis, which reveal new targets for drug development. We describe the high-resolution crystal structures of enzymes of the glyoxylate shunt, isocitrate lyase and malate synthase, and of the cyclopropane synthases of mycolic acid biosynthesis. Structure-based drug design is now underway with the potential to lead to the development of new anti-tuberculars effective against persistent and resistant Mycobacterium tuberculosis infections.

Amino Acid Sequence↗
PubMed2003

Crystal structure of Mycobacterium tuberculosis SecA, a preprotein translocating ATPase.

In bacteria, the majority of exported proteins are translocated by the Sec system, which recognizes the signal sequence of a preprotein and uses ATP and the proton motive force to mediate protein translocation across the cytoplasmic membrane. SecA is an essential protein component of this system, containing the molecular motor that facilitates translocation. Here we report the three-dimensional structure of the SecA protein of Mycobacterium tuberculosis. Each subunit of the homodimer contains a "motor" domain and a translocation domain. The structure predicts that SecA can interact with the SecYEG pore and function as a molecular ratchet that uses ATP hydrolysis for physical movement of the preprotein. Knowledge of this structure provides a framework for further elucidation of the translocation process.

Adenosine Diphosphate↗
PubMed2003

Crystal structure of ATP phosphoribosyltransferase from Mycobacterium tuberculosis.

The N-1-(5'-phosphoribosyl)-ATP transferase catalyzes the first step of the histidine biosynthetic pathway and is regulated by a feedback mechanism by the product histidine. The crystal structures of the N-1-(5'-phosphoribosyl)-ATP transferase from Mycobacterium tuberculosis in complex with inhibitor histidine and AMP has been determined to 1.8 A resolution and without ligands to 2.7 A resolution. The active enzyme exists primarily as a dimer, and the histidine-inhibited form is a hexamer. The structure represents a new fold for a phosphoribosyltransferase, consisting of three continuous domains. The inhibitor AMP binds in the active site cavity formed between the two catalytic domains. A model for the mechanism of allosteric inhibition has been derived from conformational differences between the AMP:His-bound and apo structures.

ATP Phosphoribosyltransferase↗
PubMed2003

Suicides in northern India: causes, methods used and prevention.

Suicide patterns and rates differ in various populations and cultures. It has been reported that developing countries have lower suicide rates, possibly because of a lower level of environmental stress but the Indians have a very high suicide rate (Elfawal, 1999). The choice of method used to commit suicide depends on availability of means, knowledge about lethal effectiveness, and the victim's motivation and intent. The present work was designed to investigate the different methods of self-destruction, the age and gender susceptibility to suicide, the groups particularly affected and the underlying motivating factor for such an extreme step among the North Indians. Various suggestions relating to decreasing the tensions of the modern mechanical life-style, educating the public in general and the availability, use and storage of agrochemicals have been put forward. Marriage counselling and the concept of family planning are also advocated.

Adaptation, Psychological↗
PubMed2002

Long-standing unilateral jumped facets at C3-4 with no apparent history of antecedent trauma.

We report two cases of unilateral jumped facets at C3-4 in reliable historians with no apparent history of neck trauma. Lack of associated morphological abnormalities of the associated disc, adjacent vertebral bodies, and contralateral facet essentially exclude a developmental etiology. Based on the location of the injury and the presence of chronic, osteoarthritic changes we postulate that the jumped facets were due to remote childhood trauma that was forgotten.

Journal Article↗
PubMed2002

Crystal structure of Lyme disease variable surface antigen VlsE of Borrelia burgdorferi.

VlsE is an outer surface lipoprotein of Borrelia burgdorferi that undergoes antigenic variation through an elaborate gene conversion mechanism and is thought to play a major role in the immune response to the Lyme disease borellia. The crystal structure of recombinant variant protein VlsE1 at 2.3-A resolution reveals that the six variable regions form loop structures that constitute most of the membrane distal surface of VlsE, covering the predominantly alpha-helical, invariant regions of the protein. The surface localization of the variable amino acid segments appears to protect the conserved regions from interaction with antibodies and hence may contribute to immune evasion.

Amino Acid Sequence↗
PubMed2002

Photographic documentation of spontaneous extrusion of a subconjunctival cysticercus cyst.

Spontaneous extrusion of a subconjunctival cysticercus cyst is a rare occurrence. The case reported is of a 20-year-old man who presented with a subconjunctival cysticercus cyst that was suspected to be undergoing spontaneous extrusion. The eye was photographed as the parasite extruded through the conjunctival opening with undulating movements over 3-4 min.

Adult↗